Prismatic secondary battery and assembled battery using the same

ABSTRACT

A flat-shaped winding electrode body in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween includes a positive electrode tab portion and a negative electrode tab portion at one end in a direction in which a winding axis of the winding electrode body extends. Two pieces of the flat-shaped winding electrode body are housed in a prismatic outer body so that the winding axis of each piece is disposed in a direction perpendicular to a sealing plate, and the positive electrode tab portion and the negative electrode tab portion are located on one end of the winding electrode body closer to the sealing plate than the other end.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention application claims priority to Japanese PatentApplication No. 2015-068195 filed in the Japan Patent Office on Mar. 30,2015, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to a prismatic secondary battery and anassembled battery using the prismatic secondary battery.

Description of Related Art

In drive power supplies of electric vehicles (EV) and hybrid electricvehicles (HEV, PHEV), a secondary battery such as an alkaline secondarybattery or a nonaqueous electrolyte secondary battery is used. For theseapplications, high capacity or high output characteristics is demanded,and thus an assembled battery is used in which a large number ofprismatic secondary batteries are connected in series or in parallel.

In those prismatic secondary batteries, a battery case is formed by abottomed tubular prismatic outer body having an opening, and a sealingplate that seals the opening. An electrode body including a positiveelectrode plate, a negative electrode plate, and a separator is housedin the battery case along with an electrolytic solution. A positiveelectrode terminal and a negative electrode terminal are fixed to thesealing plate. The positive electrode terminal is electrically connectedto the positive electrode plate via a positive electrode currentcollector, and the negative electrode terminal is electrically connectedto the negative electrode plate via a negative electrode currentcollector.

The positive electrode plate includes a positive electrode core made ofmetal, and a positive electrode active material layer formed on thesurface of the positive electrode core. In part of the positiveelectrode core, a positive electrode core exposed portion is formed inwhich a positive electrode active material layer is not formed. Thepositive electrode current collector is then connected to the positiveelectrode core exposed portion. Also, the negative electrode plateincludes a negative electrode core made of metal, and a negativeelectrode active material layer formed on the surface of the negativeelectrode core. In part of the negative electrode core, a negativeelectrode core exposed portion is formed in which a negative electrodeactive material layer is not formed. The negative electrode currentcollector is then connected to the negative electrode core exposedportion.

For instance, Japanese Published Unexamined Patent Application No.2009-032640 (Patent Document 1) proposes a prismatic secondary batteryusing a winding electrode body which has a positive electrode coreexposed portion wound at one end and a negative electrode core exposedportion wound at the other end. Also, Japanese Published UnexaminedPatent Application No. 2008-226625 (Patent Document 2) proposes aprismatic secondary battery using a winding electrode body which isprovided with a positive electrode core exposed portion and a negativeelectrode core exposed portion at one end.

BRIEF SUMMARY OF THE INVENTION

Regarding in-vehicle secondary batteries, particularly secondarybatteries used for EV or PHEV, development of a large-capacity secondarybattery having a higher volume energy density is called for. In the caseof the prismatic secondary battery disclosed in Patent Document 1, thebattery case needs the space on the right and left for disposing woundpositive electrode core exposed portion and wound negative electrodecore exposed portion, and needs an upper space between a sealing plateand a winding electrode body. This is a factor that makes it difficultto increase the volume energy density of the secondary battery.

On the other hand, when a winding electrode body provided with apositive electrode core exposed portion and a negative electrode coreexposed portion at one end is used as in the prismatic secondary batterydisclosed in Patent Document 2, a prismatic secondary battery having ahigh volume energy density is likely to be obtained.

However, the prismatic secondary battery disclosed in Patent Document 2is likely to have a complicated structure of the current collectorcompared with the prismatic secondary battery disclosed in PatentDocument 1.

An object of the present disclosure is to provide a high-capacityprismatic secondary battery having a high volume energy density and anassembled battery using the prismatic secondary battery.

A prismatic secondary battery according to an embodiment of the presentdisclosure includes: a flat-shaped winding electrode body in which apositive electrode plate and a negative electrode plate are wound with aseparator interposed therebetween; a prismatic outer body that has anopening and that houses the winding electrode body; a sealing plate thatseals the opening; a positive electrode terminal that is electricallyconnected to the positive electrode plate and attached to the sealingplate; a positive electrode current collector that electrically connectsthe positive electrode plate and the positive electrode terminal; anegative electrode terminal that is electrically connected to thenegative electrode plate and attached to the sealing plate; and anegative electrode current collector that electrically connects thenegative electrode plate and the negative electrode terminal. Thewinding electrode body includes a positive electrode tab portion and anegative electrode tab portion at one end in a direction in which awinding axis of the winding electrode body extends, and at least twopieces of the winding electrode body are housed in the prismatic outerbody so that the winding axis of each piece is disposed in a directionperpendicular to the sealing plate, and corresponding pieces of thepositive electrode tab portion and the negative electrode tab portionare located on one end of the winding electrode body closer to thesealing plate than the other.

With this configuration, a flat-shaped winding electrode body is used,which has one end side in which the positive electrode tab portion andthe negative electrode tab portion are formed, and which is in adirection in which the winding axis extends. The positive electrode tabportion and the negative electrode tab portion are disposed on one endof the winding electrode body closer to the sealing plate than the otherend, and thus space which is not involved in power generation may bereduced in the battery case. Therefore, a high-capacity prismaticsecondary battery having a higher volume energy density is obtained.

Furthermore, a plurality of flat-shaped winding electrode bodies ishoused in the prismatic outer body, thereby making it possible toachieve a simple structure of the connecting portion between thepositive electrode tab portion and the positive electrode currentcollector and the connecting portion between the negative electrode tabportion and the negative electrode current collector.

It is to be noted that the positive electrode current collector and thepositive electrode terminal may be integrated as one component. Thenegative electrode current collector and the negative electrode terminalmay be integrated as one component. In addition, the positive electrodecurrent collector and the positive electrode terminal may beelectrically connected via another conductive member. The negativeelectrode current collector and the negative electrode terminal may beelectrically connected via another conductive member.

Preferably, the prismatic outer body includes a bottom, a pair oflarge-area side walls, and a pair of small-area side walls, an area ofeach of the small-area side walls is smaller than an area of each of thelarge-area side walls, and an area of the bottom is smaller than thearea of each of the small-area side walls.

With this configuration, between six outer faces of the battery caseformed by the prismatic outer body and the sealing plate, the faces ofthe bottom and the sealing plate have a smaller area than other fourfaces. Therefore, it is possible to reduce the space which is formedbetween the winding electrode body and the sealing plate for disposingthe positive electrode tab portion, the negative electrode tab portion,the positive electrode current collector, and the negative electrodecurrent collector. Therefore, a prismatic secondary battery having ahigher volume energy density is achieved.

Preferably, the positive electrode plate includes a positive electrodecore, and a positive electrode active material layer formed on thepositive electrode core, the positive electrode core has a positiveelectrode core exposed portion in which the positive electrode activematerial layer is not formed, the negative electrode plate includes anegative electrode core, and a negative electrode active material layerformed on the negative electrode core, the negative electrode core has anegative electrode core exposed portion in which the negative electrodeactive material layer is not formed, the positive electrode tab portionis the positive electrode core exposed portion, and the negativeelectrode tab portion is the negative electrode core exposed portion.

The positive electrode tab portion is preferably formed of the positiveelectrode core. Also, the negative electrode tab portion is preferablyformed of the negative electrode core. It is to be noted that thepositive electrode tab portion and the negative electrode tab portioneach may be a separate component from a core connected to the positiveelectrode core or the negative electrode core. For instance, a metalplate composed of aluminum, aluminum alloy, copper, copper alloy,nickel, or nickel alloy may be used as a tab portion.

Preferably, the positive electrode tab portion includes a linear portionand a curved portion, and the negative electrode tab portion includes alinear portion and a curved portion.

Preferably, at one widthwise end of the positive electrode plate, thepieces of the positive electrode tab portion having substantially thesame width are formed at substantially regular intervals.

It is to be noted that the width of the positive electrode tab portionrefers to the width of each positive electrode tab portion in thelongitudinal direction of the positive electrode plate with the positiveelectrode plate developed. Also, the interval between the positiveelectrode tab portions refers to the distance between adjacent positiveelectrode tab portions in the longitudinal direction of the positiveelectrode plate with the positive electrode plate developed. To achievesubstantially the same width, it suffices that the widths of thepositive electrode tab portions fall in a range with ±10% difference. Itis preferable that the widths of the positive electrode tab portionsfall in a range with ±5% difference. Also, to achieve substantially thesame interval, it suffices that the intervals between adjacent positiveelectrode tab portions fall in a range with ±10% difference. It ispreferable that the intervals between adjacent positive electrode tabportions fall in a range with ±5% difference.

With this configuration, charge and discharge reactions in the positiveelectrode plate occur more uniformly. In addition, it is possible toproduce the positive electrode plate easily.

Preferably, a width of the positive electrode tab portion is ¼ a widthof the winding electrode body or greater and ½ the width of the windingelectrode body or less.

Here, the width of the winding electrode body refers to the width in thedirection perpendicular to the winding axis and perpendicular to thethickness direction of the winding electrode body.

Preferably, the pieces of the positive electrode tab portion are stackedwith a displacement, thereby forming a positive electrode steppedportion which is constituted by ends of the pieces of the positiveelectrode tab portion, and a positive electrode current collector isconnected to the positive electrode stepped portion.

Preferably, at one widthwise end of the negative electrode plate, thepieces of the negative electrode tab portion having substantially thesame width are formed at substantially regular intervals.

It is to be noted that the width of the negative electrode tab portionrefers to the width of each negative electrode tab portion in thelongitudinal direction of the negative electrode plate with the negativeelectrode plate developed. Also, the interval between the negativeelectrode tab portions refers to the distance between adjacent negativeelectrode tab portions in the longitudinal direction of the negativeelectrode plate with the negative electrode plate developed. To achievesubstantially the same width, it suffices that the widths of thenegative electrode tab portions fall in a range with ±10% difference. Itis preferable that the widths of the negative electrode tab portionsfall in a range with ±5% difference. Also, to achieve substantially thesame interval, it suffices that the intervals between adjacent negativeelectrode tab portions fall in a range with ±10% difference. It ispreferable that the intervals between adjacent negative electrode tabportions fall in a range with ±5% difference.

With this configuration, charge and discharge reactions in the negativeelectrode plate occur more uniformly. In addition, it is possible toproduce the negative electrode plate easily.

Preferably, a width of the negative electrode tab portion is ¼ the widthof the winding electrode body or greater and ½ the width of the windingelectrode body or less.

Preferably, the pieces of the negative electrode tab portion are stackedwith a displacement, thereby forming a negative electrode steppedportion which is constituted by ends of the pieces of the negativeelectrode tab portion, and a negative electrode current collector isconnected to the negative electrode stepped portion.

An assembled battery according to an aspect of the present disclosureincludes: a plurality of the prismatic secondary batteries; a pair ofend plates; and a bind bar that connects the pair of end plates. Theprismatic secondary batteries are stacked between the pair of end platesin an orientation in which the respective large-area side walls areparallel, the positive electrode terminal and the negative electrodeterminal of each of the prismatic secondary batteries are disposed onone lateral face, and a bottom of the prismatic outer body of each ofthe prismatic secondary batteries is disposed on the other lateral face.

According to the present disclosure, it is possible to provide ahigh-capacity prismatic secondary battery having a high volume energydensity and an assembled battery using the prismatic secondary battery.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a prismatic secondary batteryaccording to an embodiment;

FIG. 2 is a sectional view taken along line II-II of FIG. 1;

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 1;

FIG. 5 is a sectional view taken along line V-V of FIG. 1;

FIG. 6 is a plan view of a positive electrode plate according to theembodiment;

FIG. 7 is a plan view of a negative electrode plate according to theembodiment;

FIG. 8 is a view of a winding electrode body according to theembodiment, as seen in the direction in which a winding axis extends;

FIG. 9 is a perspective view of a current collector;

FIG. 10 is a view illustrating a process of connecting a tab portion andthe current collector;

FIG. 11 is a view illustrating a connecting portion between the tabportion and the current collector;

FIG. 12 is a view of a winding electrode body used for a prismaticsecondary battery according to a comparative example;

FIG. 13 is a view of a winding electrode body used for a prismaticsecondary battery according to the embodiment;

FIG. 14 is a perspective view of a current collector as a modification;

FIG. 15 is a perspective view of a current collector as a modification;

FIG. 16 is a perspective view of a current collector as a modification;

FIG. 17 is a perspective view of a current collector as a modification;

FIG. 18 is a view illustrating a process of connecting a tab portion anda current collector in a prismatic secondary battery as a modification;

FIG. 19 is a view illustrating a process of connecting a tab portion anda current collector in a prismatic secondary battery as a modification;

FIG. 20 is a plan view of a positive electrode plate and a negativeelectrode plate according to a modification;

FIG. 21 is a view illustrating a winding electrode body according to amodification;

FIG. 22 is a sectional view of a current cutoff mechanism of a prismaticsecondary battery according to a modification;

FIG. 23 is a perspective view of a current collector body used for thecurrent cutoff mechanism; and

FIG. 24 is a perspective view of an assembled battery according to theembodiment.

DETAILED DESCRIPTION OF THE INVENTION

The configuration of a prismatic secondary battery 20 according to anembodiment will be described below. It is to be noted that the presentdisclosure is not limited to the following embodiment.

As illustrated in FIGS. 1 to 5, the prismatic secondary battery 20includes a prismatic outer body 1 having an opening, and a sealing plate2 that seals the opening. The prismatic outer body 1 and the sealingplate 2 constitute a battery case. The prismatic outer body 1 and thesealing plate 2 are each preferably made of metal, and for instance, maybe made of aluminum or aluminum alloy. The prismatic outer body 1 has abottom 1 a, a pair of large-area side walls 1 b, and a pair ofsmall-area side walls 1 c. The prismatic outer body 1 is a bottomedtubular prismatic outer body which has an opening at a position opposedto the bottom. Flat-shaped winding electrode bodies 3, in which apositive electrode plate and a negative electrode plate are wound with aseparator interposed therebetween (those components are notillustrated), are housed in the prismatic outer body 1 together with anelectrolyte. In the positive electrode plate, a positive electrodeactive material layer including a positive electrode active material isformed on a positive electrode metal core. A positive electrode coreexposed portion 4 b, where the positive electrode core is exposed, isformed at a widthwise end of the positive electrode plate. It is to benoted that aluminum foil or aluminum alloy foil is preferably used forthe positive electrode core. In the negative electrode plate, a negativeelectrode active material layer including a negative electrode activematerial is formed on a negative electrode metal core. A negativeelectrode core exposed portion 5 b, where the negative electrode core isexposed, is formed at a widthwise end of the negative electrode plate.It is to be noted that copper foil or copper alloy foil is preferablyused for the negative electrode core. In the prismatic secondary battery20, the positive electrode core exposed portion 4 b constitutes apositive electrode tab portion 4 c, and the negative electrode coreexposed portion 5 b constitutes a negative electrode tab portion 5 c.

As illustrated in FIGS. 2 to 4, in the prismatic outer body 1, twoflat-shaped winding electrode bodies 3 are disposed so that thedirection in which the winding axis extends is perpendicular to thesealing plate 2. The positive electrode core exposed portion 4 b and thenegative electrode core exposed portion 5 b of each winding electrodebody 3 are located on one end of the winding electrode body 3 closer tothe sealing plate 2 than the other end. The positive electrode coreexposed portions 4 b of the winding electrode bodies 3 are located onthe same side (the upper side of FIG. 2), and the negative electrodecore exposed portions 5 b of the winding electrode bodies 3 are locatedon the same side (the lower side of FIG. 2).

One end side of each winding electrode body 3 in the direction in whichthe winding axis extends is provided with the stacked positive electrodecore exposed portions 4 b and the stacked negative electrode coreexposed portions 5 b. A positive electrode current collector 6 is weldedto the stacked positive electrode core exposed portions 4 b, and awelding spot 30 is formed. A positive electrode terminal 7 iselectrically connected to the positive electrode current collector 6. Anegative electrode current collector 8 is welded to the stacked negativeelectrode core exposed portions 5 b, and a welding spot 30 is formed. Anegative electrode terminal 9 is electrically connected to the negativeelectrode current collector 8.

The positive electrode terminal 7 and the positive electrode currentcollector 6 are each fixed to the sealing plate 2 via an insulatingmember 10 and a gasket 11. The negative electrode terminal 9 and thenegative electrode current collector 8 are each fixed to the sealingplate 2 via an insulating member 12 and a gasket 13. The gaskets 11, 13are disposed between the sealing plate 2 and the terminals 7, 9,respectively. The insulating members 10, 12 are disposed between thesealing plate 2 and the current collectors 6, 8, respectively. It is tobe noted that the gasket and the insulating member are preferablycomposed of an insulating resin member. Each winding electrode body 3 ishoused in the prismatic outer body 1 with covered by an insulating sheet14 which is bent in a box shape. The insulating sheet 14 covers thewinding electrode body 3 and is disposed between the winding electrodebody 3 and the prismatic outer body 1. The sealing plate 2 isweld-connected to an opening edge of the prismatic outer body 1 by laserwelding or the like. The sealing plate 2 has an electrolytic solutioninjection hole 15, which is sealed by a sealing plug 16 after injection.In the sealing plate 2, a gas exhaust valve 17 is formed for exhaustinggas when the pressure inside the battery increases.

The dimensions of the prismatic secondary battery 20 may be, forinstance, such that the width (the length in perpendicular direction tothe sealing plate 2, the length in the crosswise direction in FIG. 1) is18 cm, the thickness (the depth direction in FIG. 1) is 3 cm, and theheight (the length in parallel to the sealing plate 2 and perpendicularto the thickness direction of the prismatic secondary battery 20, thelength in the vertical direction in FIG. 1) is 9 cm. The presentdisclosure is particularly effective when the ratio of the width to theheight of the prismatic secondary battery is greater than or equal to 2.The present disclosure is particularly effective when the height of theprismatic secondary battery is 10 cm or less and the width of theprismatic secondary battery is 17 cm or greater. In addition, thepresent disclosure is particularly effective when the battery capacityis 30 Ah or higher. It is to be noted that the value of battery capacitymay be a designed capacity, that is, the value of the nominal capacityspecified by a manufacturer of batteries.

Next, a method of manufacturing the prismatic secondary battery 20 willbe described.

[Production of Positive Electrode Plate]

Positive electrode slurry including lithium cobalt oxide as a positiveelectrode active material polyvinylidene fluoride (PVdF) as a binder, acarbon material as a conductive material, and N-methylpyrrolidone (NMP)is produced. The positive electrode slurry is applied to both sides of a15 μm-thick rectangular aluminum foil which is the positive electrodecore. By drying the positive electrode slurry, the N-methylpyrrolidonein the positive electrode slurry is removed, and a positive electrodeactive material layer is formed on the positive electrode core.Subsequently, compression processing is performed so that the positiveelectrode active material layer has a predetermined thickness. Thepositive electrode plate thus obtained is cut so that the positiveelectrode core exposed portions with a predetermined width are formedwith predetermined intervals at one widthwise end of the positiveelectrode plate.

As illustrated in FIG. 6, in the positive electrode plate 4 thusobtained, a positive electrode active material layer 4 a is formed onthe positive electrode core. At one widthwise end of the positiveelectrode plate 4, positive electrode core exposed portions 4 b with apredetermined width are formed with predetermined intervals. It is to benoted that the positive electrode core exposed portions 4 b constitutethe positive electrode tab portions 4 c.

Here, width W1 of each positive electrode tab portion 4 c to 40 mm.Also, interval W2 between adjacent positive electrode tab portions 4 cis 120 mm. It is to be noted that the width W1 of the positive electrodetab portions 4 c is the width in the longitudinal direction of thepositive electrode plate.

[Production of Negative Electrode Plate]

A negative electrode slurry including black lead as a negative electrodeactive material, styrene-butadiene rubber (SBR) as a binder,carboxymethyl cellulose (CMC) as a thickening agent, and water isproduced. The negative electrode slurry is applied to both sides of a 8μm-thick rectangular copper foil which is the negative electrode core.By drying the negative electrode slurry, the water in the negativeelectrode slurry is removed, and a negative electrode active materiallayer is formed on the negative electrode core. Subsequently,compression processing is performed so that the negative electrodeactive material layer has a predetermined thickness. The negativeelectrode plate thus obtained is cut so that the negative electrode coreexposed portions with a predetermined width are formed withpredetermined intervals at one widthwise end of the negative electrodeplate.

As illustrated in FIG. 7, in the negative electrode plate 5 thusobtained, a negative electrode active material layer 5 a is formed onthe negative electrode core. At one widthwise end of the negativeelectrode plate 5, negative electrode core exposed portions 5 b with apredetermined width are formed with predetermined intervals. It is to benoted that the negative electrode core exposed portions 5 b constitutenegative electrode tab portions 5 c. The negative electrode core exposedportion 5 b are also formed at the other widthwise end of the negativeelectrode plate 5.

Here, width W3 of each negative electrode tab portion 5 c is 40 mm.Also, interval W4 between adjacent negative electrode tab portions 5 cis 120 mm. It is to be noted that the width W3 of each negativeelectrode tab is the width in the longitudinal direction of the negativeelectrode plate 5.

It is preferable that the relationship of W1+W2>2L be satisfied betweenthe width W1 of each positive electrode tab portion 4 c, the interval W2between adjacent positive electrode tab portions 4 c, length L of alinear portion of the winding electrode body 3, and radius R of a curvedportion of the winding electrode body 3. When W1+2πR<L and the startposition for rolling the positive electrode plate is 0°, it ispreferable that the start position for rolling the negative electrodeplate be 180 to 270°.

It is preferable that the relationship of W3+W4>2L be satisfied betweenthe width W2 of each negative electrode tab portion 5 c, the interval W4between adjacent negative electrode tab portions 5 c, length L of alinear portion of the winding electrode body 3, and radius R of a curvedportion of the winding electrode body 3.

[Winding Electrode Body]

The positive electrode plate 4 and the negative electrode plate 5obtained by the above-described method are slid so that no overlapoccurs between the positive electrode tab portions 4 c and the negativeelectrode tab portions 5 c, and a porous separator made of polyethyleneis interposed between the positive electrode plate 4 and the negativeelectrode plate 5, which are stacked, wound, and pressed, therebyforming the flat-shaped winding electrode body 3.

FIG. 8 is a view illustrating the surface on which the positiveelectrode tab portions 4 c and the negative electrode tab portions 5 care formed. As illustrated in FIG. 8, the positive electrode tabportions 4 c and the negative electrode tab portions 5 c are disposed onone end side of the winding electrode body 3 in the direction in whichthe winding axis extends. The positive electrode tab portions 4 c arestacked on one side of the winding electrode body 3 in the widthdirection (the direction perpendicular to the direction in which thewinding axis of the winding electrode body 3 extends, and perpendicularto the thickness direction of the winding electrode body 3), and thenegative electrode tab portions 5 c are stacked on the other side of thewinding electrode body 3.

The positive electrode tab portions 4 c and the negative electrode tabportions 5 c each have a linear portion 31 disposed on the linearportion (flat portion) of the winding electrode body 3, and a curveportion 32 disposed on a curved portion (bent portion) of the windingelectrode body 3. In addition, the positive electrode tab portions 4 care disposed and stacked to be displaced sequentially by a smalldistance from the winding start to the winding end. The negativeelectrode tab portions 5 c are also disposed and stacked to be displacedsequentially by a small distance from the winding start to the windingend. Therefore, a stepped portion 33, which is constituted by the endsof the positive electrode tab portions 4 c, is formed in the stackedpositive electrode tab portions 4 c. In addition, a stepped portion 33,which is constituted by the ends of the negative electrode tab portions5 c, is formed in the stacked negative electrode tab portions 5 c.

Two winding electrode bodies 3 thus produced are prepared and bundledsecurely by an insulating tape so that the positive electrode tabportions 4 c and the negative electrode tab portions 5 c of each windingelectrode body 3 are disposed on the same side. It is to be noted thatat least two winding electrode bodies 3 may be used and the number ofwinding electrode bodies 3 to be used is not particularly limited.Although a plurality of winding electrode bodies 3 is not necessarilyfixed, the winding electrode bodies 3 are preferably bundled securely.The bundling method is not particularly limited, and the windingelectrode bodies 3 may be secured by an insulating tape or bundled bybeing disposed in an insulating sheet which is molded in a bag shape ora box shape.

[Assembly of Sealing Plate, Current Collector, and Terminal]

As illustrated in FIGS. 1 and 2, on one end side of the sealing plate 2in the longitudinal direction, the gasket 11 is disposed on the outerside of the sealing plate 2 and the insulating member 10 is disposed onthe inner side of the sealing plate 2. The positive electrode terminal 7has a flange portion 7 a and an insert portion 7 b. The positiveelectrode terminal 7 is disposed on the gasket 11, and the positiveelectrode current collector 6 is disposed on the undersurface of theinsulating member 10. A through hole is formed in each of the gasket 11,the sealing plate 2, the insulating member 10, and the positiveelectrode current collector 6, and the positive electrode terminal 7 isinserted in each through hole and the distal end of the positiveelectrode terminal 7 is swaged, and thus the positive electrode terminal7, the gasket 11, the sealing plate 2, the insulating member 10, and thepositive electrode current collector 6 are integrally secured. It ispreferable that the swaged portion of the positive electrode terminal 7and the positive electrode current collector 6 be welded by laserwelding or the like.

On the other end side of the sealing plate 2 in the longitudinaldirection, the gasket 13 is disposed on the outer side of the sealingplate 2 and the insulating member 12 is disposed on the inner side ofthe sealing plate 2. The negative electrode terminal 9 has a flangeportion 9 a and an insert portion 9 b. The negative electrode terminal 9is disposed on the gasket 13, and the negative electrode currentcollector 8 is disposed on the undersurface of the insulating member 12.A through hole is formed in each of the gasket 13, the sealing plate 2,the insulating member 12, and the negative electrode current collector8, and the negative electrode terminal 9 is inserted in each throughhole and the distal end of the negative electrode terminal 9 is swaged,and thus the negative electrode terminal 9, the gasket 13, the sealingplate 2, the insulating member 12, and the negative electrode currentcollector 8 are integrally secured. It is preferable that the swagedportion of the negative electrode terminal 9 and the negative electrodecurrent collector 8 be welded by laser welding or the like.

The positive electrode current collector 6 and the negative electrodecurrent collector 8 illustrated in FIG. 9 are used. The positiveelectrode current collector 6 will be described as an example. Thepositive electrode current collector 6 has a base portion 6 a to beconnected to the positive electrode terminal 7, and a connecting portion6 b that extends from an end of the base portion 6 a in the direction tothe winding electrode body 3. A through hole 6 c is formed in the baseportion 6 a. The positive electrode terminal 7 is inserted in thethrough hole 6 c, and the distal end of the positive electrode terminal7 is swaged on the base portion 6 a, thereby connecting the positiveelectrode terminal 7 and the positive electrode current collector 6. Theconnecting portion 6 b is provided in both ends (the end on the nearside and the end on the far side in FIG. 9) of the base portion 6 a inthe thickness direction of the battery. A projection 34 is formed ineach connecting portion 6 b. Also, a slit 35 is formed in the connectingportion 6 b. The negative electrode current collector 8 may also havethe same shape as that of the positive electrode current collector 6.The positive electrode current collector 6 and the negative electrodecurrent collector 8 are preferably formed by bending a plate-like metalmember.

[Connection of Current Collector and Winding Electrode Body]

FIG. 10 is a view illustrating a process of connecting a tab portion anda current collector, and is a sectional view corresponding to FIG. 2 andFIG. 3. As illustrated in FIG. 10, in each of one surface side and theother surface side, the positive electrode tab portions 4 c are disposedwhich are stacked on the projection 34 formed in the connecting portion6 b of the positive electrode current collector 6. With the stackedpositive electrode tab portions 4 c and the positive electrode currentcollector 6 interposed between a pair of resistance welding electrodes40, a resistance welding current is fed and resistance welding isperformed. Thus, the stacked positive electrode tab portions 4 c and thepositive electrode current collector 6 are weld-connected. For thenegative electrode side also, the negative electrode tab portions 5 cand the negative electrode current collector 8 are weld-connected in thesame manner.

When the positive electrode current collector 6 or the negativeelectrode current collector 8 illustrated in FIG. 9 is used, weldingconnection is first performed on the portions where the projection 34 isformed on the near left side and on the far side of FIG. 9, by themethod illustrated in FIG. 10. Subsequently, welding connection isperformed on the portions where the projection 34 is formed on the nearright side and on the far side of FIG. 9, by the method illustrated inFIG. 10. At this point, since the slit 35 is formed in each connectingportion 6 b as illustrated in FIG. 9, when resistance welding isperformed on the second spot, generation of reactive current (a currentwhich is not involved in the resistance welding) passing through thefirst welding spot which has undergone resistance welding may beavoided. It is to be noted that with regard to the order of performingresistance welding, either the left side or the right side in FIG. 9 maybe the first spot, or both sides may be the first spot at the same time.The same method may also be applied to the negative electrode side.

As illustrated in FIG. 11, the positive electrode current collector 6may be weld-connected to the stepped portion 33 of the positiveelectrode tab portions 4 c. This allows the positive electrode currentcollector 6 to be more securely connected to not only the positiveelectrode tab portions 4 c located on the outermost circumference of thewinding electrode body 3, but also the positive electrode tab portions 4c located on the inner circumferential side of the winding electrodebody 3. In addition, not only the positive electrode tab portions 4 clocated on the outermost circumference of the winding electrode body 3,but also the positive electrode tab portions 4 c located on the innercircumferential side of the winding electrode body 3 are welded atpositions near the positive electrode current collector 6. Therefore,current may be collected more uniformly. The same method may also beapplied to the negative electrode side.

Next, the winding electrode body 3 connected to the positive electrodecurrent collector 6 and the negative electrode current collector 8 isinserted in the prismatic outer body 1 with installed in the insulatingsheet 14 bent in a box shape. The joint portion between the sealingplate 2 and the prismatic outer body 1 is then welded by laser welding,and the opening of the prismatic outer body 1 is sealed. Subsequently, anonaqueous electrolyte is injected from the electrolysis solutioninjection hole 15 provided in the sealing plate 2, and the electrolysissolution injection hole 15 is sealed by the sealing plug 16, therebyproducing the prismatic secondary battery 20.

In the prismatic secondary battery 20, the positive electrode tabportions 4 c and the negative electrode tab portions 5 c are eachdisposed on one end of the winding electrode body 3 closer to thesealing plate 2 than the other end in the winding electrode body 3.Therefore, space for disposing members not involved in power generationmay be reduced in the prismatic outer body 1, and thus a prismaticsecondary battery having a high volume energy density is achieved. Inaddition, in the prismatic secondary battery 20, the sealing plate 2 isdisposed on the face with the smallest area, which is one of six facesof the battery case constituted by the prismatic outer body 1 and thesealing plate 2. In other words, the sealing plate 2 and the bottom 1 aof the prismatic outer body 1 have an area smaller than the area of eachof four side walls (a pair of large-area side walls 1 b and a pair ofsmall-area side walls 1 c) of the prismatic outer body 1. Consequently,space for disposing members not involved in power generation may bereduced, and a prismatic secondary battery having a higher volume energydensity is achieved.

Furthermore, in the prismatic secondary battery 20, a plurality offlat-shaped winding electrode bodies 3 is housed in the prismatic outerbody 1.

When a prismatic secondary battery with a larger capacity (for instance,a battery capacity of 30 Ah or higher) is produced, if a single windingelectrode body is housed in the prismatic outer body 1, the windingelectrode body has a large number of winding and an increased thicknessas illustrated in FIG. 12. In such a winding electrode body, positionalignment of the positive electrode tab portions 4 c and of the negativeelectrode tab portions 5 c is difficult, and it is also difficult toincrease the width of each positive electrode tab portion 4 c andnegative electrode tab portion 5 c. In addition, there is a possibilitythat the positive electrode tab portions 4 c and the negative electrodetab portions 5 c are likely to come into contact with each other.Furthermore, connection between the positive electrode tab portions 4 cand the positive electrode current collector 6, and connection betweenthe negative electrode tab portions 5 c and the negative electrodecurrent collector 8 are difficult to make.

In contrast to this, housing a plurality of flat-shaped windingelectrode bodies 3 in the prismatic outer body 1 makes it easy toperform position alignment of the positive electrode tab portions 4 cand of the negative electrode tab portions 5 c. Also, contact betweenthe positive electrode tab portions 4 c and the negative electrode tabportions 5 c may be easily prevented by increasing the width of eachpositive electrode tab portion 4 c and negative electrode tab portion 5c (see FIG. 13). Therefore, dividing the electrode body to be housed inthe prismatic outer body 1 into multiple pieces as in the prismaticsecondary battery 20 allows the width of each positive electrode tabportion 4 c and negative electrode tab portion 5 c to be increased whilepreventing contact between the positive electrode tab portions 4 c andthe negative electrode tab portions 5 c, thereby improving the currentcollection efficiency. Furthermore, it is possible to protect thepositive electrode tab portions 4 c and the negative electrode tabportions 5 c against damage and fracture due to vibration. Consequently,a highly reliable prismatic secondary battery having a superior currentcollection efficiency is obtained.

First Modification

FIG. 14 illustrates a current collector according to a firstmodification. In the positive electrode current collector 6 (thenegative electrode current collector 8), the projection 34 provided ineach connecting portion 6 b (8 b) may be a linear projection thatextends in a horizontal direction. With this configuration, thepositional displacement of the resistance welding electrodes 40 withrespect to the projection 34 at the time of welding may be allowed.Thus, a current collection structure having a higher productivity and asuperior welding quality is achieved.

Second Modification

FIG. 15 illustrates a current collector according to a secondmodification. In the positive electrode current collector 6 (thenegative electrode current collector 8), a portion where a welding spotis formed may be provided on each of the near side and the far side.Also, the projection 34 may also be punctiform (such as square,circular, hemispherical). Also, the base portion 6 a (8 a) has awide-width portion 6 a 1 (8 a 1) which has a large width in thethickness direction of the prismatic secondary battery 20, and anarrow-width portion 6 a 2 (8 a 2) which has a smaller width than thewide-width portion 6 a 1 (8 a 1) in the thickness direction of theprismatic secondary battery 20. The positive electrode terminal 7 (thenegative electrode terminal 9) is connected to the wide-width portion 6a 1 (8 a 1). The connecting portions 6 b (8 b) are formed at ends of thenarrow-width portion 6 a 2 (8 a 2). With this configuration, the area ofthe portion in the base portion 6 a (8 a), connected to the positiveelectrode terminal 7 (the negative electrode terminal 9) can beenlarged, and thus workability of connecting the positive electrodeterminal 7 (the negative electrode terminal 9) to the base portion 6 a(8 a) improves. Since the area with both ends including a pair ofconnecting portions 6 b (8 b) can be small in the base portion 6 a (8a), deformation of the base portion 6 a (8 a) may be reduced when thepositive electrode current collector 6 (the negative electrode currentcollector 8) is interposed between a pair of resistance weldingelectrodes at the time of resistance welding.

Third Modification

FIG. 16 illustrates a current collector according to a thirdmodification. As illustrated, the narrow-width portions 6 a 2 (8 a 2)may be provided at both sides of the wide-width portion 6 a 1 (8 a 1).Also, each of both sides of one narrow-width portions 6 a 2 (8 a 2) maybe provided with the connecting portions 6 b (8 b), and each of bothsides of the other narrow-width portion 6 a 2 (8 a 2) may be providedwith the connecting portions 6 b (8 b).

Fourth Modification

FIG. 17 illustrates a current collector according to a fourthmodification. The positive electrode terminal 7 (the negative electrodeterminal 9) may be connected to the base portion 6 a (8 a) by welding orthe like in advance. When such a current collector is used, the positiveelectrode terminal 7 (the negative electrode terminal 9) is inserted ina through hole of the sealing plate 2 from the inner side of thebattery, and the positive electrode terminal 7 (the negative electrodeterminal 9) is fixedly swaged to an external conductive member disposedon the outer side of the battery.

Fifth Modification

FIG. 18 illustrates a process of connecting the positive electrodecurrent collector 6 and the positive electrode tab portions 4 c in aprismatic secondary battery according to a fifth modification. Asillustrated in FIG. 18, a current collector receiving component 41 maybe disposed on an outer surface of stacked positive electrode tabportions 4 c, the outer surface being on the opposite side to the sidewhere the connecting portion 6 b of the positive electrode currentcollector 6 is disposed. The current collector receiving component 41has a first area 41 a disposed along the positive electrode tab portions4 c, and a bent portion 41 b which is formed at an end of the first area41 a, the end being closer to the winding electrode body 3 than theother end. When the bent portion 41 b is formed, even if sputteringoccurs at the time of resistance welding, scattering of sputteredmaterial toward a power generation unit (portion where the positiveelectrode plate 4 and the negative electrode plate 5 are stacked) of thewinding electrode body 3 and damage to the power generation unit may beavoided.

Sixth Modification

FIG. 19 illustrates a process of connecting the positive electrodecurrent collector 6 and the positive electrode tab portions 4 c in aprismatic secondary battery according to a fifth modification. In thepositive electrode current collector 6, a spacer 42 may be disposedbetween the connecting portion 6 b on one side and the connectingportion 6 b on the other side. Thus, when the stacked positive electrodetab portions 4 c and the connecting portions 6 b of the positiveelectrode current collector 6 are interposed between the pair ofresistance welding electrodes 40, deformation of the positive electrodecurrent collector 6 may be reduced. It is to be noted that the spacer 42may be composed of a metal member or a resin member. The spacer 42 ispreferably an insulating resin member. Also, the spacer 42 may beplate-shaped, block-shaped, or pillar-shaped.

The details of the embodiment and modifications described above areapplicable to each of the positive electrode side and the negativeelectrode side.

In the embodiment and modifications described above, an example has beenillustrated in which connection between the positive electrode tabportions and the positive electrode current collector and connectionbetween the negative electrode tab portions and the negative electrodecurrent collector are made by resistance welding. However, theconnection may also be made by another method. For instance, instead ofthe resistance welding, ultrasonic welding or welding by high energyrays such as a laser may be used.

Seventh Modification

The following configuration may be adopted to a winding electrode bodyaccording to a modification. FIG. 20 is a plan view of the positiveelectrode plate 54 (the negative electrode plate 55). In the positiveelectrode plate 54 (the negative electrode plate 55), a positiveelectrode active material layer 54 a (55 a) is formed on the positiveelectrode core (the negative electrode core). Positive electrode coreexposed portions 54 b (negative electrode core exposed portions 55 b)are formed at both ends of the positive electrode plate 54 (the negativeelectrode plate 55) in the longitudinal direction. A positive electrodetab 56 (a negative electrode tab 57) is connected by welding to each ofthe positive electrode core exposed portions 54 b (the negativeelectrode core exposed portions 55 b). The positive electrode tab 56(the negative electrode tab 57) is preferably a metal plate having athickness greater than that of the positive electrode core (the negativeelectrode core).

The positive electrode plate 54 and the negative electrode plate 55 likethis are wound with a separator interposed therebetween, and aflat-shaped winding electrode body 60 is formed in which each of thepositive electrode tabs 56 and the negative electrode tabs 57 projectsfrom one end in the axial direction of flat-shaped winding (FIG. 21).Then using a plurality of such flat-shaped winding electrode bodies 60,it is possible to produce a prismatic secondary battery. For instance,the flat-shaped winding electrode bodies 60 are stacked and used in theorientation of FIG. 21. In this case, it is preferable that four or moreflat-shaped winding electrode bodies 60 be used. By using four or moreflat-shaped winding electrode bodies 60 like this, a prismatic secondarybattery, which avoids the reduction in current collection performanceand yet has a high volume energy density, is achieved.

It is to be noted that the widths X2 and X3 of the positive electrodetab 56 and the negative electrode tab 57 are each preferably ¼ the widthX1 of the flat-shaped winding electrode body 60 or greater. This enablesthe reduction of internal resistance and a prismatic secondary batteryhaving an improved vibration resistance is achieved. In order to achievea prismatic secondary battery having a further improved vibrationresistance, it is preferable that the positive electrode tab 56(negative electrode tab 57) be disposed from one end E1 to the other endE2 crossing a center line C in the width direction of the positiveelectrode plate 54 (the negative electrode plate 55) as illustrated inFIG. 20. This enables the winding electrode body 60 to be securelyconnected to the sealing plate via the positive electrode tabs 56 andthe negative electrode tabs 57.

<Current Cutoff Mechanism>

Either one of a conductive path between the positive electrode plate andthe positive electrode terminal and a conductive path between thenegative electrode plate and the negative electrode terminal may beprovided with a current cut-off mechanism that operates with increasinginternal pressure of the battery and blocks the conductive path betweenthe positive electrode plate and the positive electrode terminal or theconductive path between the negative electrode plate and the negativeelectrode terminal to cut off the current. In this case, the operatingpressure of a gas exhaust valve preferably has a value greater than theoperating pressure of the current cut-off mechanism.

The current cut-off mechanism preferably includes a deformation platethat deforms with increasing internal pressure of the battery, and abreaking portion that breaks due to deformation of the deformationplate. The breaking portion is preferably formed in the positiveelectrode current collector. In this case, for instance, the positiveelectrode current collector may be the positive electrode currentcollector 6 illustrated in FIG. 15. In the positive electrode currentcollector 6, a thin-walled portion or a notched portion is formed as thebreaking portion in the periphery of the through hole 6 c. A deformationplate is disposed above the base portion 6 a of the positive electrodecurrent collector 6. The periphery of the through hole 6 c is thenweld-connected to the lower surface of the deformation plate by laserwelding or the like. Thus, when the deformation plate is deformed upwardwith increasing internal pressure of the battery, the thin-walledportion or the notched portion provided in the base portion 6 a breaksand a conductive path is cut off. In such a case, connection between thepositive electrode tab portions 4 c and the positive electrode currentcollector 6 is preferably made by resistance welding. Thus, in contrastto the case where the positive electrode tab portions 4 c and thepositive electrode current collector 6 are ultrasonic-welded, adverseeffect of vibration on the breaking portion may be reduced. Also, incontrast to the case where the positive electrode tab portions 4 c andthe positive electrode current collector 6 are laser-welded, adverseeffect of sputtering on the breaking portion may be reduced. Inaddition, due to the formation of the wide-width portion 6 a 1 (8 a 1),a breaking portion may be easily formed. When an insulating member isdisposed between the deformation plate and the base portion 6 a, and theinsulating member and the base portion 6 a are fixed, the wide-widthportion 6 a 1 (8 a 1) allows easy fixing. As a method for this, forinstance, a through hole or a notch is provided in the wide-widthportion 6 a 1 (8 a 1), and a projection formed in the insulating membermay be fitted into the through hole or the notch. Also, a portion in thebase portion, where the connecting portion 6 b is formed, is thenarrow-width portion 6 a 2, and so when the positive electrode tabportions 4 c are connected to the connecting portion 6 b, deformation ofthe base portion 6 a is reduced, and thus the degree of damage on thebreaking portion may be reduced.

FIG. 22 illustrates a sectional view of a prismatic secondary batteryhaving the current cut-off mechanism. It is to be noted that thesectional view corresponds to the enlarged view of the positiveelectrode terminal and its periphery in FIG. 2. A cup-shaped conductivemember 60 having a tubular portion is disposed on the lower surface ofthe insulating member 10. Near the insulating member 10, the conductivemember 60 has a through hole, in which the positive electrode terminal 7is inserted, and the conductive member 60 is connected to the positiveelectrode terminal 7. The conductive member 60 has an opening on theinner side of the battery. The deformation plate 61 is disposed so as toblock the opening. The peripheral edge of the deformation plate 61 isweld-connected to the conductive member 60, and the opening is sealed bythe deformation plate 61. The positive electrode current collector 6 isconnected to the surface, on the inner side of the battery, of thedeformation plate 61. The positive electrode current collector 6 has athrough hole 63, the edge of which is weld-connected to the deformationplate 61. In the periphery of a portion which is weld-connected, athin-walled portion 64 is formed. A circular groove 65 is formed in thethin-walled portion 64. When the pressure inside the battery increases,a central portion of the deformation plate 61 is deformed so as to moveupward toward the sealing plate 2. In conjunction with this, theconnecting portion between the deformation plate 61 and the positiveelectrode current collector 6 is pulled toward the sealing plate 2 andthe circular groove 65 breaks. Thus, the conductive path between thepositive electrode plate and the positive electrode terminal 7 is cutoff and charging current is blocked. This enables the protection againstfurther development of overcharge.

It is to be noted that an insulating plate 62 made of resin is disposedbetween the deformation plate 61 and the positive electrode currentcollector 6. The insulating plate 62 is latched and fixed to aninsulating plate 10 (not illustrated). The insulating plate 62 has aprojection 67 for fixation, and the projection 67 is inserted in athrough hole 66 for fixation formed in the positive electrode currentcollector 6, and the diameter of the end of the projection 67 isexpanded. Thus, the insulating plate 62 and the base portion 6 a of thepositive electrode current collector 6 are connected and fixed.

FIG. 23 is a perspective view of the positive electrode currentcollector 6 used for the current cut-off mechanism. It is to be notedthat FIG. 22 corresponds to a sectional view taken along line XXII-XXIIof FIG. 23. The positive electrode current collector 6 has the baseportion 6 a and the connecting portions 6 b that extend from the baseportion 6 a toward the electrode body. The base portion 6 a has awide-width portion 6 a 1 which has a large width in the thicknessdirection (the direction of the shorter side of the sealing plate) ofthe prismatic secondary battery, and a narrow-width portion 6 a 2 whichhas a smaller width than the wide-width portion 6 a 1 in the thicknessdirection of the prismatic secondary battery. In the wide-width portion6 a 1, the base portion 6 a is connected to the deformation plate 61.Also, in the wide-width portion 6 a 1, the base portion 6 a is fixed tothe insulating plate 62. The connecting portions 6 b are provided in thenarrow-width portion 6 a 2.

With the current cut-off mechanism thus formed, when the positiveelectrode tab portions 4 c are weld-connected to the connecting portions6 b of the positive electrode current collector 6, adverse effect on afragile portion (expected breaking portion) provided in the base portion6 a, and the connecting portion between the deformation plate 61 and thebase portion 6 a may be reduced. For instance, scattering of sputteredmaterial to the fragile portion or the connecting portion may bereduced, the sputtered material being generated at the time of weldingthe connecting portions 6 b and the positive electrode tab portions 4 c.Or deformation of the periphery of the fragile portion and theconnecting portion in the base portion 6 a is reduced due to stress atthe time of welding the connecting portions 6 b and the positiveelectrode tab portions 4 c. It is preferable that the relationship ofW1/W2≥3/2 be satisfied between the width W1 of the wide-width portion 6a 1 and the width W2 of the narrow-width portion 6 a 2.

It is to be noted that the current cut-off mechanism in thisconfiguration is effective even when a single winding electrode body ishoused in the prismatic outer body. In addition, the current cut-offmechanism in this configuration is effective even when stacked electrodebodies are housed in the prismatic outer body.

The following configuration may be adopted for an assembled batteryusing a plurality of prismatic secondary batteries 20.

As illustrated in FIG. 24, in an assembled battery 50, a plurality ofprismatic secondary batteries 20 is stacked between a pair of end plates51 in an orientation in which respective large-area side walls areparallel. The pair of end plates 51 are connected by a bind bar 52. Itis to be noted that the end plates and a bus bar are connected using abolt or a rivet or by welding. An insulating separator 53 is disposedbetween the prismatic secondary batteries 20, and the separator 53 ispreferably composed of a resin. In the assembled battery 50, thepositive electrode terminal 7 and the negative electrode terminal 9 ofeach prismatic secondary battery 20 are disposed on one lateral face(the lateral face on the near side in FIG. 24). Terminals of adjacentprismatic secondary batteries 20 are connected by a bus bar 54. Thebottom of each prismatic secondary battery 20 is disposed on the otherlateral face (the lateral face on the far side in FIG. 24). Thesmall-area side walls of each prismatic secondary battery 20 aredisposed on the upper surface and the lower surface of the assembledbattery 50. By adopting this configuration, a low-height assembledbattery having an extremely high volume energy density is achieved. Theassembled battery 50 thus constructed is mounted in a vehicle in theorientation illustrated in FIG. 24, thereby achieving significantlyimproved occupant comfort in the vehicle.

It is to be noted that a cooling plate 55, in which a cooling mediumflows, is disposed in the bottom surface of the assembled battery 50,and each prismatic secondary battery 20 is preferably cooled by thecooling plate. It is to be noted that the cooling medium may be a gas ora liquid.

While detailed embodiments have been used to illustrate the presentinvention, to those skilled in the art, however, it will be apparentfrom the foregoing disclosure that various changes and modifications canbe made therein without departing from the spirit and scope of theinvention. Furthermore, the foregoing description of the embodimentsaccording to the present invention is provided for illustration only,and is not intended to limit the invention.

What is claimed is:
 1. A prismatic secondary battery comprising: a firstflat-shaped winding electrode body in which a first positive electrodeplate and a first negative electrode plate are wound with a firstseparator interposed therebetween; a second flat-shaped windingelectrode body in which a second positive electrode plate and a secondnegative electrode plate are wound with a second separator interposedtherebetween; a prismatic outer body that has an opening and that housesthe first flat-shaped winding electrode body and the second flat-shapedwinding electrode body; a sealing plate that seals the opening; apositive electrode terminal that is electrically connected to the firstpositive electrode plate and the second positive electrode plate andattached to the sealing plate; a positive electrode current collectorthat electrically connects the first positive electrode plate and thesecond positive electrode plate and the positive electrode terminal; anegative electrode terminal that is electrically connected to the firstnegative electrode plate and the second negative electrode plate andattached to the sealing plate; and a negative electrode currentcollector that electrically connects the first negative electrode plateand the second negative electrode plate and the negative electrodeterminal, wherein the first flat-shaped winding electrode body includesa plurality of first positive electrode tab portions and a plurality offirst negative electrode tab portions at one end in a direction in whicha winding axis of the first flat-shaped winding electrode body extends,and wherein the second flat-shaped winding electrode body includes aplurality of second positive electrode tab portions and a plurality ofsecond negative electrode tab portions at one end in a direction inwhich a winding axis of the second flat-shaped winding electrode bodyextends, the first flat-shaped winding electrode body and the secondflat-shaped winding electrode body are housed in the prismatic outerbody so that the winding axis of the first flat-shaped winding electrodebody and the winding axis of the second flat-shaped winding electrodebody are disposed in a direction substantially perpendicular to thesealing plate, the plurality of first positive electrode tab portionsand the plurality of first negative electrode tab portions are locatedon one end of the first flat-shaped winding electrode body closer to thesealing plate than the other end, and the plurality of second positiveelectrode tab portions and the plurality of second negative electrodetab portions are located on one end of the second flat-shaped windingelectrode body closer to the sealing plate than the other end, whereinthe positive electrode current collector includes a first connectingportion connected to the positive electrode terminal, and a secondconnecting portion welded to the plurality of first positive electrodetab portions, the first connecting portion is spaced away from thesecond connecting portion in a longitudinal direction of the sealingplate, and a distance between the sealing plate and the secondconnecting portion is greater than a distance between the sealing plateand the first connecting portion in the direction substantiallyperpendicular to the sealing plate.
 2. The prismatic secondary batteryaccording to claim 1, wherein the prismatic outer body includes abottom, a pair of large-area side walls, and a pair of small-area sidewalls, an area of each of the small-area side walls is smaller than anarea of each of the large-area side walls, and an area of the bottom issmaller than the area of each of the small-area side walls.
 3. Theprismatic secondary battery according to claim 1, wherein the firstpositive electrode plate includes a positive electrode core, and apositive electrode active material layer formed on the positiveelectrode core, the positive electrode core has a positive electrodecore exposed portion in which the positive electrode active materiallayer is not formed, the first negative electrode plate includes anegative electrode core, and a negative electrode active material layerformed on the negative electrode core, the negative electrode core has anegative electrode core exposed portion in which the negative electrodeactive material layer is not formed, the first positive electrode tabportion is the positive electrode core exposed portion, and the firstnegative electrode tab portion is the negative electrode core exposedportion.
 4. The prismatic secondary battery according to claim 1,wherein the first positive electrode tab portion includes a linearportion and a curved portion, and the first negative electrode tabportion includes a linear portion and a curved portion.
 5. The prismaticsecondary battery according to claim 1, wherein at one widthwise end ofthe first positive electrode plate, the plurality of first positiveelectrode tab portions having substantially the same width are formed atsubstantially regular intervals.
 6. The prismatic secondary batteryaccording to claim 1, wherein a width of the first positive electrodetab portion is ¼ a width of the first flat-shaped winding electrode bodyor greater and ½ the width of the first flat-shaped winding electrodebody or less.
 7. The prismatic secondary battery according to claim 1,wherein the plurality of first positive electrode tab portions arestacked with a displacement, thereby forming a positive electrodestepped portion which is constituted by ends of the plurality of firstpositive electrode tab portions, and the positive electrode currentcollector is connected to the positive electrode stepped portion.
 8. Theprismatic secondary battery according to claim 1, wherein at onewidthwise end of the first negative electrode plate, the plurality offirst negative electrode tab portions having substantially the samewidth are formed at substantially regular intervals.
 9. The prismaticsecondary battery according to claim 1, wherein a width of the firstnegative electrode tab portion is ¼ the width of the first flat-shapedwinding electrode body or greater and ½ the width of the firstflat-shaped winding electrode body or less.
 10. The prismatic secondarybattery according to claim 1, wherein the plurality of first negativeelectrode tab portions are stacked with a displacement, thereby forminga negative electrode stepped portion which is constituted by ends of theplurality of first negative electrode tab portions, and the negativeelectrode current collector is connected to the negative electrodestepped portion.
 11. An assembled battery comprising a plurality of theprismatic secondary batteries according to claim 1, the assembledbattery comprising: a pair of end plates; and a bind bar that connectsthe pair of end plates, wherein the prismatic secondary batteries arestacked between the pair of end plates in an orientation in which therespective large-area side walls are parallel, the positive electrodeterminal and the negative electrode terminal of each of the prismaticsecondary batteries are disposed on one lateral face, and a bottom ofthe prismatic outer body of each of the prismatic secondary batteries isdisposed on the other lateral face.
 12. The prismatic secondary batteryaccording to claim 1, wherein the positive electrode current collectorincludes a base portion and a connecting portion, the connecting portioncomprises a bent end portion extending from the base portion, aninsulating member is disposed between the sealing plate and the baseportion, the positive electrode terminal is connected to the baseportion, and the plurality of first positive electrode tab portions arestacked upon each other and welded to the connecting portion.
 13. Theprismatic secondary battery according to claim 12, wherein the firstpositive electrode tab portion is longer than the connecting portion ofthe positive electrode current collector in a longitudinal direction ofthe sealing plate.
 14. The prismatic secondary battery according toclaim 1, wherein the plurality of first positive electrode tab portionsare stacked upon each other and welded to the positive electrode currentcollector to form a first connecting portion, the plurality of secondpositive electrode tab portions are stacked upon each other and weldedto the positive electrode current collector to form a second connectingportion, and the first connecting portion is spaced away from the secondconnecting portion in a short-side direction of the sealing plate. 15.The prismatic secondary battery according to claim 1, wherein theplurality of first positive electrode tab portions are stacked upon eachother and are collectively disposed between, and welded to, the positiveelectrode current collector and a current collector receiving component.16. The prismatic secondary battery according to claim 1, wherein thepositive electrode current collector includes a base portion, and aconnecting portion that comprises a bent end portion extending from thebase portion, the positive electrode terminal is connected to the baseportion, the plurality of first positive electrode tab portions arestacked upon each other and welded to the connecting portion, and theplurality of first positive electrode tab portions are collectivelydisposed between, and welded to, the positive electrode currentcollector and a current collector receiving component.
 17. The prismaticsecondary battery according to claim 1, wherein the first flat-shapedwinding electrode body includes a pair of opposed planar outer surfacesextending substantially parallel to each other, and a pair of opposedcurved outer surfaces connecting the pair of opposed planar outersurfaces to each other, the first flat-shaped winding electrode bodydefines a first plane that includes the winding axis of the firstflat-shaped winding electrode body and extends substantially parallel tothe pair of opposed planar outer surfaces, and an aggregate volume ofthe plurality of first positive electrode tab portions present on oneside of the first plane is greater than an aggregate volume of theplurality of first positive electrode tab portions present on the otherside of the first plane.
 18. The prismatic secondary battery accordingto claim 1, wherein the plurality of first positive electrode tabportions each have a length substantially identical to each other in alongitudinal direction of the sealing plate, and edges of the pluralityof first positive electrode tab portions are displaced relative to eachother in the longitudinal direction of the sealing plate to form astepped portion therealong.
 19. An assembled battery comprising aplurality of the prismatic secondary batteries according to claim 2, theassembled battery comprising: a pair of end plates; and a bind bar thatconnects the pair of end plates, wherein the prismatic secondarybatteries are stacked between the pair of end plates in an orientationin which the respective large-area side walls are parallel, the positiveelectrode terminal and the negative electrode terminal of each of theprismatic secondary batteries are disposed on one lateral face, a bottomof the prismatic outer body of each of the prismatic secondary batteriesis disposed on the other lateral face, a cooling plate is disposed on abottom of the assembled battery, the cooling plate containing a coolingmedium, the winding axis of the first flat-shaped winding electrode bodyand the winding axis of the second flat-shaped winding electrode bodyare substantially parallel to the bottom of the assembled battery, andthe one lateral face where the positive electrode terminal and thenegative electrode terminal of each of the prismatic secondary batteriesare disposed extends substantially perpendicular to the bottom of theassembled battery.